Design of D-A1-A2 Covalent Triazine Frameworks via Copolymerization for Photocatalytic Hydrogen Evolution

Conjugated porous polymers (CPPs) have recently emerged as prospective materials for photocatalytic hydrogen evolution. In the design of CPP photocatalysts, one of the challenges is to find ways to inhibit backward charge recombination and promote forward charge transfer/separation. Conjugated donor-acceptor polymers are capable of favoring forward intramolecular charge separation; however, they often suffer from backward charge recombination simultaneously, which causes a decrease of the quantum efficiency for solar-energy conversion. Herein, a photoinduced electron-transfer system via constructing D-A(1)-A(2) conjugated polymers for photocatalytic hydrogen evolution is developed. Such a D-A(1)-A(2) system can not only boost charge separation but also suppress charge recombination owing to the cascade energy levels of the comprised units and large charge delocalization structures. Therefore, an apparent quantum yield up to 22.8% at 420 nm is achieved, and the highest hydrogen evolution rate can be up to 966 mu mol h(-1) (19.3 mmol g(-1) h(-1)) under visible light irradiation. These values are comparable to the state-of-the-art CPPs as well as part of inorganic photocatalysts. This work provides an alternative strategy and insight for the design of CPP photocatalytic systems for photocatalytic applications in high efficiency.